The purpose of the studies of red cell and granulocyte membranes, outlined in this proposal, is to define changes in cell membrane protein and lipid metabolism which may influence cell flexibility and permeability. The flexibility and permeability of erythrocytes is crucial to cell survival in vivo and is also particularly relevant to the problem of prolonged erythrocyte storage. Particular attention is focused upon the role of the Red cell membrane protein Spectrin since defects in Spectrin appear to be a common denominator in several clinical Hemolytic disorders.